Fig. 3. Localization of brain-derived neurotrophic factor (BDNF) and trkB (the high-affinity neurotrophin receptor of brain-derived neurotrophic factor) mRNA and protein within the preovulatory follicle. In situ hybridization and immunocytochemical detection shows BDNF mRNA (A) and protein (B) expression, respectively, within the theca interna of the F1 follicle (arrows). By comparison, in situ hybridization shows trkB mRNA (C) localized within the theca interna and granulosa layers (arrows), while expression of the TrkB protein (D) is localized to the basement membrane side of the granulosa cell layer and to a lesser extent within the theca interna (arrows). (E) A negative control for in situ hybridization using a non-sense cDNA probe; (F) a negative control for immunolocalization using preimmune serum. The scale bars are graded in µm. Y, yolk; Gr, granulosa layer; BM, basement membrane (arrowhead); Ti, theca interna; Te, theca externa.